EP3315214B1 - Method for epilame coating of a timepiece or piece of jewellery - Google Patents

Description

Field of the invention

The present invention relates to the field of mechanics and in particular to the field of watchmaking or jewelry. It relates more particularly to a method of epilamating at least part of a surface of a substrate present in a timepiece or jewelry.

Invention background

There are different methods for modifying the surface condition of a substrate by treatment with an appropriate agent so as to specifically improve certain surface properties. For example, in the field of mechanics, and in particular in the field of watchmaking, but also in the field of jewelry, the epilamage of a surface of a part or of an element is often carried out means of an epilam agent in order to control and reduce the surface energy of said surface during its use. More particularly, the purpose of an epilam agent is to prevent the spreading of oils or lubricants on the elements of a timepiece or of jewelry by forming an invisible hydrophobic and lipophobic molecular layer on the surface of the element allowing the lubricant to remain at a predetermined location on the treated surface and thus avoid its spreading. Maintaining the lubricant in its operating zone increases its durability.

At present, the vast majority of epilame agents available on the market, such as Fixodrop® FK / BS from Moebius® or the Fluorad ™ range from 3M ™ (FC-722 and others), consists of a dissolved fluoropolymer in a perfluorinated or fluorinated solvent. The epilamation process is traditionally carried out by dipping (dip coating) of the parts to epilamate in a depilamation bath consisting of a solution of perfluorinated or fluorinated solvent loaded with epilam agent.

The most widely used fluorinated solvents until recently were 3M ™ tetradecafluorohexane and HFE-7100. However, tetradecafluorohexane in particular has the drawback of constituting, once volatilized, a greenhouse gas, since it remains stable 3200 years in the air and has a greenhouse effect potential of 7400 CO ₂ equivalent.

The use of such solvents having been prohibited by new environmental regulations, new fluorinated solvents have been developed. However, even if these new generation fluorinated solvents (such as 3M ™ HFE-7200) are less stable in the air, they still have an impact on the environment. They therefore require the use of closed machines or other equipment and are likely to be impacted by even more stringent future regulations. In addition, these new generation fluorinated solvents are relatively expensive.

To replace the traditional depilating process using polluting and expensive fluorinated solvents, demand EP 1,927,648 proposes a process of epilamage with a solution of epilame molecule in a water / propanol mixture. This depilating process has the drawback of being able to be used only with a very limited number of epilam agents since the epilam molecules must be soluble in the water / propanol mixture. However, it is well known to those skilled in the art that the best epilamous properties are obtained with fluorinated molecules which therefore have very low solubility in a water / propanol mixture.

Finally, the epilam agent concentrations used in the traditional depilating process by soaking are very low (typically between 20 mg / L and 250 mg / L) and the fluorinated solvents used are volatile (boiling temperature below 100 ° VS). As a result, the industrial management of hair removal baths is complex on a daily basis because it is necessary to regularly control the concentration of agent by dosing. epilam in the epilamage bath and add a concentrated solution of epilame agent or solvent depending on the evolution of the composition of the epilamage bath.

Of the document DE 10 2013 226 215 , a process is known for epilamating at least part of the surface of a substrate according to the preamble of claim 1.

Summary of the invention

The object of the invention is in particular to overcome the various drawbacks of the known epilamation processes.

More specifically, an objective of the invention is to provide a new epilamage process making it possible to obtain an epilamage of identical or higher quality than that obtained with a traditional epilamage process by soaking.

Another object of the invention is to provide a new ecological epilamation process making it possible to eliminate the use of a large quantity of polluting fluorinated solvents.

Another object of the invention is to provide a new economical epilamation process which makes it possible to eliminate the use of a large quantity of expensive fluorinated solvents.

The object of the invention is also to provide a new depilamation process making it possible to simplify the daily management of the depilamation baths.

1. a) préparation d'un agent épilame
2. b) optionnellement, préparation de la surface du substrat
3. c) placement du substrat et de l'agent épilame dans une enceinte à pression ambiante
4. d) introduction dans l'enceinte fermée hermétiquement de CO₂ à une pression comprise entre 25 bar et 74 bar et à une température comprise entre 10°C et 80°C pendant une durée comprise entre 1 min et 30 min,
5. e) diminution de la pression dans l'enceinte, et
6. f) sortie du substrat épilamé de l'enceinte,

le procédé étant caractérisé en ce que l'agent épilame est sous forme d'une solution dans un solvant, sa concentration dans le mélange solvant/CO₂ étant comprise entre 10 mg et 5 g pour 1000 g de mélange (CO₂+solvant), de préférence entre 50 mg et 1 g pour 1000 g de mélange (CO₂+solvant), encore plus préférentiellement entre 100 mg et 500 mg pour 1000 g de mélange (CO₂+solvant).To this end, the present invention relates to a process for epilamating at least part of a surface of a substrate comprising the steps of:

1. a) preparation of an epilam agent
2. b) optionally, preparation of the substrate surface
3. c) placing the substrate and the epilam agent in an enclosure at ambient pressure
4. d) introduction into the hermetically sealed enclosure of CO ₂ at a pressure between 25 bar and 74 bar and at a temperature between 10 ° C and 80 ° C for a period between 1 min and 30 min,
5. e) reduction of the pressure in the enclosure, and
6. f) leaving the epilamated substrate from the enclosure,

the method being characterized in that the epilam agent is in the form of a solution in a solvent, its concentration in the solvent / CO ₂ mixture being between 10 mg and 5 g per 1000 g of mixture (CO ₂ + solvent) , preferably between 50 mg and 1 g per 1000 g of mixture (CO ₂ + solvent), even more preferably between 100 mg and 500 mg per 1000 g of mixture (CO ₂ + solvent).

According to the invention, CO ₂ is used in a form close to supercritical conditions to convey the epilam agent and to deposit an invisible hydrophobic and oleophobic molecular layer of said epilam agent. Thus, the method according to the invention drastically decreases or even no longer requires the use of fluorinated solvent, so that the method of the invention is ecological and economical, while preserving the quality of epilamage.

Detailed description of the invention

The depilamation process relates to the deposition of a layer of an epilam agent on the surface of a substrate generally belonging to an element of a timepiece or of jewelry intended to be in contact with a lubricating agent. The epilam agent layer forms an invisible hydrophobic and oleophobic molecular layer, making it possible to avoid spreading of the lubricant.

1. a) préparation d'un agent épilame
2. b) optionnellement, préparation de la surface du substrat
3. c) placement du substrat et de l'agent épilame dans une enceinte à pression ambiante, soit une pression comprise entre 0.6 bar et 1.1 bar, et fermeture hermétique de l'enceinte
4. d) introduction dans l'enceinte fermée hermétiquement de CO₂ à une pression comprise entre 25 bar et 74 bar, de préférence entre 45 bar et 70 bars, et plus préférentiellement entre 50 bar et 60 bar, et à une température comprise entre 10°C et 80°C, et de préférence entre 25°C et 60°C, et plus préférentiellement entre 30°C et 50°C, pendant une durée comprise entre 1 min et 30 min, de préférence entre 1 min et 20 min, et plus préférentiellement entre 3 min et 15 min,
5. e) diminution de la pression dans l'enceinte, et
6. f) sortie du substrat épilamé de l'enceinte.

According to the invention, the process for epilamating at least part of a surface of said substrate comprises the steps of:

1. a) preparation of an epilam agent
2. b) optionally, preparation of the substrate surface
3. c) placing the substrate and the epilam agent in an enclosure at ambient pressure, ie a pressure of between 0.6 bar and 1.1 bar, and hermetically closing the enclosure
4. d) introduction into the hermetically sealed enclosure of CO ₂ at a pressure between 25 bar and 74 bar, preferably between 45 bar and 70 bar, and more preferably between 50 bar and 60 bar, and at a temperature between 10 ° C and 80 ° C, and preferably between 25 ° C and 60 ° C, and more preferably between 30 ° C and 50 ° C, for a period of between 1 min and 30 min, preferably between 1 min and 20 min, and more preferably between 3 min and 15 min,
5. e) reduction of the pressure in the enclosure, and
6. f) exit of the epilamated substrate from the enclosure.

In general, according to step b), the substrate surface must be thoroughly cleaned before epilamation to be perfectly clean. All suitable surface preparation treatments known to those skilled in the art can be used. However, advantageously, step b) may comprise a treatment of the surface of the substrate with CO ₂ at a temperature between 10 ° C and 80 ° C and a pressure between 25 bar and 250 bar, for one duration between 1 min and 60 min. Such a treatment allows in particular the elimination of particulate dust and the degreasing of the surface. Advantageously, the treatment according to stage b) is carried out in the same enclosure as that provided for stage d), which makes it possible to be able to chain the various stages of the process of the invention while avoiding any manipulation of the rooms. In this case, the enclosure in which the substrate has been placed is closed for the implementation of step b), then opened to place the epilam agent therein according to step c) then closed again for the implementation from step d).

In a particularly advantageous manner, any known epilam agent can be used in the process of the invention. Preferably, the agent epilame is a fluoropolymer, and advantageously the epilame agent is chosen from the group of epilame agents described in the patent application EP 3,070,133 from the same depositor. By this choice, it is advantageous to obtain an epilam film which withstands horological washing.

According to a first variant of implementation not claimed, the epilam agent can be placed in the enclosure in a pure form.

According to a second implementation variant according to the invention, the epilam agent can be placed in the enclosure in the form of a solution in a solvent. Depending on the volume of the enclosure and the CO ₂ pressure, an adequate volume and concentration of the solution of epilam agent will be determined so as to have a concentration of the epilam agent in the solvent / CO ₂ mixture between 10 mg and 5 g per 1000 g of mixture (CO ₂ + solvent), preferably between 50 mg and 1 g per 1000 g of mixture (CO ₂ + solvent), even more preferably between 100 mg and 500 mg per 1000 g of mixture (CO ₂ + solvent).

Preferably, said solvent is an organic solvent, preferably a fluorinated solvent, and more preferably a perfluoroolefin.

Therefore, when the epilam agent is in solution in a fluorinated solvent, the quantity of fluorinated solvent used in the process of the invention is very small compared to the quantity used for a traditional epilamage bath.

Preferably, the reduction in the pressure in the enclosure during step e) takes place slowly, for a period of between a few seconds and a few minutes, for example between 5 s and 10 min. Advantageously, the CO ₂ is recovered and recycled. Advantageously, the epilam agent is recovered and reused for the epilamation of a subsequent batch.

Preferably, the depilamation process according to the invention further comprises, between steps e) and f), an additional step g) heat treatment of the epilamated substrate. For example, the epilamated substrate is heated in the enclosure at a temperature between 30 ° C and 80 ° C for a period between 2 min and 30 min. Such a heat treatment makes it possible to improve the anchoring of the epilam agent to the surface of the treated substrate.

Advantageously, the surface of the substrate, at least part of which is covered with the epilam agent, is made of a material chosen from the group comprising metals, metal oxides, polymers, sapphire, ruby, silicon, oxides of silicon, silicon nitrides, silicon carbides, DLC (Diamond Like Carbon), and their alloys.

More specifically, the surface of the substrate can be made of steel, or of noble metals such as gold, rhodium, palladium, platinum, or of metal oxides, doped or not with aluminum, zirconium, titanium, chromium, manganese, magnesium, iron. , nickel, copper, zinc, molybdenum, silver, tungsten, as well as their alloys, or in polyoxymethylene or acrylamide.

The method according to the invention allows batch processing of the parts. In addition, all of the different stages can be carried out in a single enclosure, which avoids unnecessary manipulation. The method according to the invention makes it possible to eliminate the use of a depilating bath based on polluting and expensive fluorinated solvent, and moreover to remove any control of the depilating bath. It is therefore ecological, economical, and easy to implement. In addition, the method according to the invention makes it possible to obtain a quality of epilamage at least identical to the quality obtained with a traditional epilamage process by dipping. In particular, the substrates treated according to the process of the invention show no residual trace of epilam agent, the efficacy of the epilam agent is similar and the resistance to washing of the deposited epilam agent is at least identical.

The following examples illustrate the present invention without, however, limiting its scope.

A compound described in the publication is used as the epilam agent. EP 3,070,133 from the same depositor, with the formula shown below:

Procedures used: Preparation of substrates :

Before the epilam treatment, substrates of different types are cleaned by standard watchmaking processes. More particularly, the parts are cleaned with a solution of Rubisol in the presence of ultrasound, rinsed several times with isopropyl alcohol, then dried with hot air.

Epilamous treatment of substrates according to the invention (CO ₂ assisted):

• des substrats de différente nature à épilamer
• 30 mL d'une solution d'agent épilame à 1g/L dans le Vertrel Suprion L'autoclave est fermé puis 225mL de CO₂ à une pression de 55 bars et à une température de 40°C sont introduits dans l'autoclave. La durée d'épilamage est fixée à 10 min puis l'autoclave est dépressurisé lentement (temps de dépressurisation 40s) et chauffé à 65°C pendant 15 min. Enfin les substrats épilamés sont récupérés et analysés.

In accordance with the invention, the following are introduced into an autoclave (255 mL):

• substrates of different kinds to epilate
• 30 mL of a solution of epilam agent at 1g / L in Vertrel Suprion The autoclave is closed and then 225mL of CO ₂ at a pressure of 55 bars and at a temperature of 40 ° C are introduced into the autoclave. The epilamation time is fixed at 10 min then the autoclave is depressurized slowly (depressurization time 40 s) and heated at 65 ° C for 15 min. Finally, the epilamated substrates are recovered and analyzed.

Comparative example: Epilamage by the dip-coating process

The substrates are epilamated by immersion (approximately 5 min) in a solution of the epilam agent (structure indicated above) (solvent: Vertrel® Suprion ™ from DuPont ™ at 250 mg / L) then drying with hot air.

Effectiveness and property of hair removal: - Aesthetic aspect:

The substrates epilamated according to the process of the invention (assisted CO ₂ ) and the comparative process (dip coating) are checked by eye. In both cases, the epilame film is invisible.

- Contact angles:

The effectiveness of the epilam agent is evaluated by depositing drops of lubricants: MOEBIUS 9010 oil. The contact angle between the substrates and the lubricant was measured on a Dataphysics device of OCA type.

The results are as follows: Substrates Hair removal process Sapphire Steel Gold Or Rh Polyethylene oxide CO ₂ assisted (inv.) 85 86 87 84 82 84 Dip coating (comp.) 81 83 85 78 78 87

- Resistance to washing

The resistance to washing of epilamous agents is evaluated after 3 successive washes (standard watch washing with a solution of Rubisol) of the epilamated parts.

The results are as follows: Substrates Hair removal process Sapphire Steel Gold Or Rh Polyethylene oxide CO ₂ assisted (inv.) 78 83 83 70 65 85 Dip coating (comp.) 77 82 78 48 71 73

Conclusion:

The above results show that the contact angles obtained just after epilamage and after three watch washings with 9010 oil are comparable between the process of the invention (assisted CO ₂ ) and the comparative process (dip coating). In certain cases (Ni or POM substrates), the resistance to washing of the epilam agent is even slightly higher when the latter is deposited by the process of the invention. This shows that the dip coating process, which consumes a lot of solvent, can be advantageously replaced by a CO ₂ assisted depilating process according to the invention, which is ecological and economical, without degradation of performance (depilamation and resistance of hair removal).

Claims (7)

1. Epilamization method of at least one part of a substrate surface comprising the steps of:

   a) preparing an epilame agent,

   b) optionally, preparing the substrate surface,

   c) placing the substrate and the epilame agent in a chamber at ambient pressure,

   d) introducing CO₂ into the hermetically sealed chamber at a pressure comprised between 25 bar and 74 bar, preferably between 45 bar and 70 bar, and more preferably between 50 bar and 60 bar, and at a temperature comprised between 10°C and 80°C, and preferably between 25°C and 60°C, and more preferably between 30°C and 50°C, for a duration comprised between 1 minute and 30 minutes, preferably between 1 minute and 20 minutes, and more preferably between 3 minutes and 15 minutes,

   e) reducing the pressure in the chamber, and

   f) removing the epilamized substrate from the chamber,

   the method being characterized in that the epilame agent is in the form of a solution in a solvent, the concentration thereof in the solvent/CO₂ mixture being comprised between 10 mg and 5 g per 1000 g of mixture (CO₂+solvent), preferably between 50 mg and 1 g per 1000 g of mixture (CO₂+solvent), more preferably between 100 mg and 500 mg per 1000 g of mixture (CO₂+solvent).
2. Epilamization method according to claim 1, characterized in that the method further comprises, between steps e) and f), a step g) of heat treatment of the epilamized substrate.
3. Epilamization method according to any of the preceding claims, characterized in that step b) comprises a CO₂ treatment at a temperature comprised between 10°C and 80°C and a pressure comprised between 25 bar and 250 bar.
4. Epilamization method according to claim 1, characterized in that the solvent is a fluorinated solvent.
5. Epilamization method according to any of the preceding claims, characterized in that the epilame agent is fluorinated polymer.
6. Epilamization method according to any of the preceding claims, characterized in that the surface of the substrate, at least part of which is coated with the epilame agent, is made of a material chosen from the group comprising metals, metal oxides, polymers, sapphire, ruby, silicon, silicon oxides, silicon nitrides, silicon carbides, DLC (Diamond like carbon), and alloys thereof.
7. Epilamization method according to any of the preceding claims, characterized in that the substrate belongs to an element of a timepiece or of a piece of jewellery.